Light-emitting diode chip

ABSTRACT

A LED chip including a first semiconductor layer; an active layer; a second semiconductor layer; a plurality of indentations, wherein each indentation extends downward to reach and expose the first semiconductor layer, wherein each indentation includes a bottom part and two side surfaces in a cross sectional view; an exposing area exposing the first semiconductor layer at a side of the LED chip; a first metal layer disposed on the second semiconductor layer and electrically connecting to the first semiconductor layer; and a first insulating layer formed between the first metal layer and the second semiconductor layer to isolate the first metal layer from the second semiconductor layer; wherein the first metal layer continuously extends to the plurality of indentations, covers the bottom part, the two side surfaces of each indentation and a top surface of the second semiconductor layer around the two side surfaces and contacts the exposing area; and wherein the first metal layer includes a plurality of recesses corresponding to the plurality of indentations.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. patentapplication Ser. No. 14/826,646, filed on 14 Aug. 2015, which is aContinuation application of U.S. patent application Ser. No. 13/715,120,filed on 14 Dec. 2012, for which priority is claimed under 35 U.S.C. §120; and this application claims priority of Application No. 101101147filed in Taiwan on 11 Jan. 2012 under 35 U.S.C. § 119, the entirecontents of all of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Fields of the Invention

The present invention relates to a light-emitting diode (LED) chip,especially to an LED chip comprising indirectly overlapped metal layerswhich are branched and distributed over a surface of the LED chip.

2. Descriptions of Related Art

A light-emitting diode (LED) is a light source made from semiconductormaterials such as III-V group of semiconductors including galliumphosphide, gallium arsenide, etc. When a voltage is applied to thesemiconductor, electrons and holes meet and recombine under electrodevoltage difference. At this moment, the electrons fall to the lowerenergy level and the energy is released in the form of photons. Theelectric power is converted to light that is emitted out.

Due to exhaustion of non-renewable resources including coal, naturalgas, petroleum, etc, energy saving products also need developmentbesides developing new energy sources to slow down consumption of fossilfuels. Under the pressure of unstable oil prices, countries worldwideare dedicated to develop energy saving products. Thus technologies oflight-emitting diode, a so-called green light source, become more matureover time, and the application fields thereof get broader. Right nowLED's have been widely used in indicators and display of computer,communication and consumer electronics (3C) products. Along withincreasing yield rate of LED's, manufacturing cost per each unit of LEDis significantly reduced, prompting adoption of LED as lighting materialin various fields.

As mentioned above, since development of high brightness LED has been aresearch emphasis of manufacturers in most countries, how to furtherenhance the efficiency of the LED shall be the focus to be stressed forimprovement.

Refer to FIG. 1, a lateral light-emitting diode chip basically comprisesa substrate 10, a first semiconductor layer 11, an active layer 12, asecond semiconductor layer 13, a first electrode 40 and a secondelectrode 41. As shown in the figure, the first semiconductor layer 11which is an n-type semiconductor is disposed on the substrate 10, andthe active layer 12 is disposed on the first semiconductor layer 11.Then the second semiconductor layer 13 which is a p-type semiconductoris disposed on the active layer 12. The first electrode 40 and thesecond electrode 41 are respectively disposed on the first semiconductorlayer 11 and the second semiconductor layer 13. While in use, anexternal voltage is applied to the light-emitting diode chip through theelectrodes to make the active layer 12 emit light. Because the currenttends to traverse the shortest pathway, the current flows downwardvertically from the second electrode 41 through the second semiconductorlayer 13 and then arrives the active layer 12. Such that the mainemission area of the active layer 12 is restricted to a region justbelow the second electrode 41 and the neighborhood. As to the areafarther, the emission efficiency thereof is lowered due to less currentpassed.

SUMMARY OF THE INVENTION

The present application provides a light-emitting diode (LED) chipincluding a first semiconductor layer; an active layer disposed on thefirst semiconductor layer; a second semiconductor layer disposed on theactive layer; a plurality of indentations, wherein each indentationextends downward to reach the first semiconductor layer and exposes thefirst semiconductor layer, wherein each indentation includes a bottompart and two side surfaces in a cross sectional view; an exposing areaexposing the first semiconductor layer at a side of the LED chip; afirst metal layer disposed on the second semiconductor layer andelectrically connecting to the first semiconductor layer; and a firstinsulating layer deposited on the second semiconductor layer and betweenthe first metal layer and the second semiconductor layer to isolate thefirst metal layer from the second semiconductor layer; wherein the firstmetal layer continuously extends to the plurality of indentations,covers the bottom part, the two side surfaces of each indentation and atop surface of the second semiconductor layer around the two sidesurfaces and contacts the exposing area; and wherein the first metallayer includes a plurality of recesses corresponding to the plurality ofindentations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing showing structure of an LED chip;

FIG. 2 is a schematic drawing showing a cross section of the embodimentaccording to the present invention;

FIG. 3 is a schematic drawing showing a cross section of the embodimentcomprising an indentation according to the present invention;

FIG. 4 is a schematic drawing showing a top view of the embodimentwithout the transparent conductive layer according to the presentinvention;

FIG. 5 is a schematic drawing showing a top view of the embodimentaccording to the present invention;

FIG. 6 is a schematic drawing showing a cross section of line A-A′ ofFIG. 5 according to the present invention;

FIG. 7 is a schematic drawing showing a cross section of line B-B′ ofFIG. 5 according to the present invention; and

FIG. 8 is a schematic drawing showing a cross section of line C-C′ ofFIG. 5 according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment according to the present invention, as shown in FIG. 2 andFIG. 3, is an LED chip comprising a substrate 10, a first semiconductorlayer 11 deposited on the substrate 10, an active layer 12 deposited onthe portion of the semiconductor layer 11, a second semiconductor layer13 deposited on the active layer 12, at least one indentation 20(Another embodiment comprises a plurality of indentation 20) comprisinga bottom part 201 deposited on the second semiconductor layer 13; afirst insulating layer 30, a first metal layer 31, a second insulatinglayer 32, a transparent conductive layer 33, and a second metal layer 34deposited on the second semiconductor layer 13 sequentially. Wherein thebottom part 201 of indentation 20 extends downward to reach the firstsemiconductor layer 11.

Further, the first insulating layer 30 is disposed on a portion of thesecond semiconductor layer 13 to separated the first metal layer 31 andthe second semiconductor layer 13 as shown in FIG. 2. At the position ofthe indentation 20 as shown in FIG. 3, the first semiconductor layer 11is exposed at the bottom part 201, the first metal layer 31 is disposedon the first insulating layer 30 at the bottom part 201 of theindentation 20, so that the first metal layer 31 can electricallyconnects to the first semiconductor layer 11. The second insulatinglayer 32 covers at least a portion of the first metal layer 31. Thetransparent conductive layer 33 is disposed on the second semiconductorlayer 13 and the second insulating layer 32, and the second metal layer34 is disposed on the second transparent conductive layer 33 and thesecond insulating layer 32.

According to the structure of the present invention described forward,while the first metal layer 31 is disposed on the second semiconductorlayer 13, the first metal layer 31 is isolated by the first insulatinglayer 30 and the second insulating layer 32. And while the first metallayer 31 proceeds to the bottom part 201 of the indentation 20, thefirst metal layer 31 connects to the first semiconductor layer 11smoothly because the first insulating layer 30 does not extend to thebottom part 201, thereby achieving the goal of current spreading.

FIG. 4 is a schematic drawing showing a top view of the embodiment ofthe present invention without the transparent conductive layer 33 andthe second metal layer 34. As shown in the figure, the LED chip of thepresent invention further comprises a first electrode 40 which connectedto the first metal layer 31 deposited on the first semiconductor layer11, and a plurality of the indentations 20 are distributed over thesurface of the LED chip wherein the bottom part 201 of each indentationexposes the first semiconductor layer 11 which originally covered by theactive layer 12 and the second semiconductor layer 13. The LED chipfurther comprises a branched-strip metal cover region which distributedlike fingers is disposed on the second semiconductor layer 13, where thefirst insulating layer 30 is disposed thereon and along edges of theindentations 20 without passing through the bottom parts 201. So thatthe first metal layer 31 deposited on the insulating layer 30 will notcontact the active layer 12 or the second semiconductor layer 13resulting in short circuit. In other words, under electrical isolationfrom the second semiconductor layer 13 by the first insulating layer 30,the first metal layer 31 deposited on the first insulating layer 30 canstill connects to the first semiconductor layer 11 at the bottom parts201 of the indentations 20.

FIG. 5 is a schematic drawing showing a top view of the embodiment ofthe present invention as illustrated in FIG. 4 further deposited thetransparent conductive layer 33, the second metal layer 34, and thesecond electrode 41. As shown in the figure, the LED chip of the presentinvention further comprises a second electrode 41 which connected to thesecond metal layer 34 deposited on the transparent conductive layer 33which completely covered the second semiconductor layer 13, and thesecond insulating layer 32 deposited between the first metal layer 31and the second metal layer 34. Wherein the transparent conductive layer33 further covered the second insulating layer 32, the first metal layer31, and the first insulating layer 30.

Regarding to material of the structure of the embodiment describedforward, when the first semiconductor layer 11 is an n-typesemiconductor layer, the second semiconductor layer 13 is a p-typesemiconductor layer. And accordingly, the first electrode 40 is ann-type electrode and the second electrode 41 is a p-type electrode. Onthe other hand, when the first semiconductor layer 11 is a p-typesemiconductor layer, the second semiconductor layer 13 is an n-typesemiconductor layer; and the first electrode 40 is a p-type electrode,the second electrode 41 is an n-type electrode. And the transparentconductive layer 33 comprises indium tin oxide that is a mixture ofindium oxide (In₂O₃) and tin oxide (SnO₂). Generally, the mass ratio ofthe mixture is 90% In₂O₃ and 10% SnO₂. When indium tin oxide is in afilm form, it is transparent and conductive. Thus, light emitted fromthe active layer 12 can pass the transparent conductive layer 33smoothly. Moreover, due to conductivity of the transparent conductivelayer 33, current generated by the voltage applied to the second metallayer 34 can flow to the second semiconductor layer 13 throughconduction of the transparent conductive layer 33.

In order to disclose the structure of the LED chip of the presentinvention in more detail, the cross sections at line A-A′, B-B′, andC-C′ of FIG. 5 are illustrated as backward.

As shown in FIG. 6, the cross section at the line A-A′ of FIG. 5illustrated the structure of indentation 20 of the LED chip of thepresent invention, the first metal layer 31 connects to the firstsemiconductor layer 11 at the bottom part 201. The first insulatinglayer 30 effectively isolates the first metal layer 31 from the secondsemiconductor layer 13 or the active layer 12, so that the LED chip canoperate normally under the structure comprising indentations.

As shown in FIG. 4 to FIG. 6, the LED chip of the present inventioncomprises the first metal layer 31 and the second metal layer 34 whichare arranged into an indirect overlapping structure and electricallyisolated with each other by the second insulating layer 32. And themetal layers with the indirect overlapping structure are branched intoseveral strips like fingers and distributed on the surface of the LEDchip, then the electric current can be distributed and flows moreevenly, which increasing not only the emission area of the active layer12 but also the emission efficiency. In order to achieve the indirectoverlapping, the shape and volume of the overlapped portions of thefirst metal layer 31 and the second metal layer 34 are the same, and thefirst metal layer 31 and the second metal layer 34 comprise metalcompound. In order to decrease and avoid any possible shielding on theactive layer 12 caused by stacking of the metal layers there above, thefirst metal layer 31 and the second metal layer 34 are overlapped mostlyand precisely from the top view of the LED chip of the present inventionto ensure the light extraction efficiency.

As shown in FIG. 7, the cross section at the line B-B′ of FIG. 5illustrated the structure at the position of the first electrode 40 ofthe LED chip of the present invention, the first electrode 40 disposedon the first semiconductor layer 11 is located on one side of the LEDchip, and connects to the first metal layer 31 along the firstinsulating layer 30 which separated/isolated the electrode 40 and thefirst metal layer 31 from the second semiconductor layer 13 and theactive layer 12 to prevent short circuit.

As shown in FIG. 8, the cross section at the line C-C′ of FIG. 5illustrated the structure at the position of the second electrode 41 ofthe LED chip of the present invention, the second electrode 41 disposedon the transparent conductive layer 33 is located on the other side ofthe LED chip, and connects to the second metal layer 34. The firstelectrode 40 and the second electrode 41 are positioning for wirebonding of the LED chip with adjacent LED chips or a power source. Bybonding wires made of gold, a voltage can be applied to the LED chip ofthe present invention to emit light.

According to the present invention as illustrated forward, the firstmetal layer 31 electrically connects to the first semiconductor layer 11at the bottom part 201 of each indentation 20. Then the current can flowalong a path formed by the second metal layer 34, the transparentconductive layer 33, the second semiconductor layer 13, the active layer12, the first semiconductor layer 11, and the first metal layer 31, soas to make the active layer 12 emit light evenly and enhancing the lightemission efficiency. Because the voltage applied is distributed evenlyby the branched-strip design, the region far away from the center of theLED can still get the same voltage supply through the branched-stripdistribution of the overlapped metal layers. And there is needless toreduce the area of the active layer 12 and the second semiconductorlayer 13 greatly for exposing the electrode on the first semiconductorlayer 11. Therefore the present invention increases a ratio of the areaof the active layer 12 to that of the overall chip, the light extractionarea the light extraction efficiency.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A light-emitting diode (LED) chip, comprising: afirst semiconductor layer; an active layer disposed on the firstsemiconductor layer; a second semiconductor layer disposed on the activelayer; a plurality of indentations, wherein each indentation extendsdownward to reach the first semiconductor layer and exposes the firstsemiconductor layer, wherein each indentation comprises a bottom partand two side surfaces in a cross sectional view; an exposing areaexposing the first semiconductor layer at a side of the LED chip; afirst metal layer disposed on the second semiconductor layer andelectrically connecting to the first semiconductor layer; and a firstinsulating layer formed on the second semiconductor layer and betweenthe first metal layer and the second semiconductor layer to isolate thefirst metal layer from the second semiconductor layer; wherein the firstmetal layer continuously extends to the plurality of indentations,covers the bottom part, the two side surfaces of each indentation and atop surface of the second semiconductor layer around the two sidesurfaces and contacts the exposing area; and wherein the first metallayer comprises a plurality of recesses corresponding to the pluralityof indentations.
 2. The LED chip as claimed in claim 1, furthercomprising a second metal layer disposed on the second semiconductorlayer and above the first metal layer.
 3. The LED chip as claimed inclaim 1, wherein the plurality of the indentations distributed over asurface of the LED chip.
 4. The LED chip as claimed in claim 2, furthercomprising a second insulating layer disposed on the first metal layerand between the first metal layer and the second metal layer to isolatethe first metal layer from the second metal layer.
 5. The LED chip asclaimed in claim 1, further comprising a transparent conductive layerformed on the second semiconductor layer.
 6. The LED chip as claimed inclaim 1, wherein the first insulating layer is disposed along the sidesurfaces of each indentation.
 7. The LED chip as claimed in claim 1,wherein the first metal layer covers the side surfaces of each indentionto connect to the first semiconductor layer.
 8. The LED chip as claimedin claim 1, further comprising a substrate under the first semiconductorlayer, and wherein the first semiconductor layer comprises a sidesurface connecting to the exposing area and the side surface of thefirst semiconductor layer connects to a side surface of the substrate.